7.7.37 Target Identification
29.0603GPPGeneral Packet Radio Service (GPRS)GPRS Tunnelling Protocol (GTP) across the Gn and Gp interfaceRelease 17TS
The Target Identification information element contains the identification of a target RNC. Octets 4-n shall a non-transparent copy of the corresponding IEs (see clause 7.7.A) and be encoded as specified in Figure 51 below. The "Target RNC-ID" part of the "Target ID" parameter is specified in 3GPP TS 25.413 [7].
NOTE 1: The ASN.1 parameter "Target ID" is forwarded non-transparently in order to maintain backward compatibility.
NOTE 2: For GERAN/UTRAN to E-UTRAN relocation, the Target ID received on the Iu interface may be either the eNB-ID or the Corresponding RNC-ID of the relocation target. If the eNB-ID is received on the Gb/Iu interface, the eNB-ID is mapped to the corresponding RNC-ID and sent in the Forward Relocation Request message. The mapping between the Corresponding RNC-ID and the actual eNB-ID of the relocation target is defined by the network operator and is outside the scope of this specification. Preferably the Target RNC ID used for an eNodeB contains the LAI and RAC mapped from the GUMMEI of the MME serving the target eNodeB as specified within TS 23.003 [2]. This avoids configuration of additional identity resolutions and also guarantees that LAIs used for E-UTRAN and UTRAN are mutually exclusive.
NOTE 3: The preamble of the "Target RNC-ID" (numerical value of e.g. 0x20) however shall not be included in octets 4-n. Also the optional "IE-Extensions" parameter shall not be included into the GTP IE.
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Bits |
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Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
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1 |
Type = 138 (Decimal) |
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2 to 3 |
Length = n |
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4 |
MCC digit 2 |
MCC digit 1 |
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5 |
MNC digit 3 |
MCC digit 3 |
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6 |
MNC digit 2 |
MNC digit 1 |
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7 to 8 |
LAC |
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9 |
RAC (see NOTE) |
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10 to 11 |
RNC-ID |
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a to (a+1) |
Extended RNC-ID (optional) |
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Figure 51: Target Identification Information Element
If only two digits are included in the MNC, then bits 5 to 8 of octet 5 (MNC digit 3) shall be coded as "1111".
The location area code (LAC) consists of 2 octets. Bit 8 of octet 7 is the most significant bit and bit 1 of octet 8 is the least significant bit. The coding of the location area code is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.
The RNC-ID consists of 2 octets and contains 12 bits long value (see 3GPP TS 25.413 [7]). Bit 4 of octet 10 is the most significant bit and bit 1 of octet 11 is the least significant bit (bits 8 to 5 of octet 10 are set to 0). The coding of the RNC-ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used.
The Extended RNC-ID consists of 2 octets and contains 16 bits long value within the range 4096 to 65535. Bit 8 of octet a is the most significant bit and bit 1 of octet (a+1) is the least significant bit. The coding of the Extended RNC-ID is the responsibility of each administration. Coding using full hexadecimal representation (binary, not ASCII encoding) shall be used. If the optional Extended RNC-ID is included, then the receiver shall ignore the RNC-ID.
If the optional Extended RNC-ID is not included, then the length variable ‘n’ = 8 and the overall length of the IE is 11 octets. Otherwise, ‘n’ = 10 and the overall length of the IE is 13 octets.
NOTE: In the "TargetRNC-ID" ASN.1 type definition in 3GPP TS 25.413 [7] the "RAC" parameter is marked as optional. RAC is however always available at an SGSN/MME when it sends the RAC in e.g. a GTPv1 Forward Relocation Request message.